A site has $S_S=0\mathrm{.}75(g)$ and $S_1=0\mathrm{.}35(g).$ The average shear wave velocity in the top $100$ ft of soil is $2000f\frac{t}{sec}.$ What is $S_{M1}$ for the site?

$($a$)0\mathrm{.}47$ g

$($b$)0\mathrm{.}53$ g

$($c$)0\mathrm{.}58$ g

$($d$)0\mathrm{.}64$ g